1. Field of the Invention
The present invention relates generally to railcar trucks and more particularly to a lightweight railcar truck bolster.
2. Description of the Related Art
Railcar trucks are the wheeled vehicles that ride on the tracks and support the railcar body. Two trucks are normally used beneath each car body. Each truck includes wheel sets which includes two wheels spaced transversely from each other and joined by a transversely extending axle. Journal bearings are pressed onto each of the axle. Transversely spaced side frames are supported on the wheel sets. The side frames are longitudinally elongated and define longitudinally spaced, downwardly opening pedestal jaws. Bearing adapters are mounted in the jaws and the adapters rotatably receive the wheel set journal bearings. The wheel sets and side frames are mounted together by the bearing adapters.
Transversely extending between each side frame is a truck bolster. The truck bolster includes a center bowl and two opposed, elongated bolster arms that extend transversely outward from beneath the center bowl. The arms and the bolster overall, are formed of a top plate, also known as a compression member, a bottom plate, also known as a tension member, and two upright structural or side walls. The bolster arms extend outward a length such that in service, the bolster arms extend through bolster arm openings in the side frames. The truck bolster is mounted on helical springs which are also mounted in the bolster arm openings and supported on the side frames. The helical springs support the weight of the railcar and payload and cushion the shock caused by uneven railroad track.
The Association of American Railroads (xe2x80x9cA.A.R.xe2x80x9d) sets forth structural requirements for truck bolsters. These requirements include the truck bolster being strong enough to support the weight of the railcar and its payload and also exhibit fatigue resistant capabilities for extended service of the bolster. Because the railcar truck bolsters must exhibit high strength, truck bolsters are conventionally made of cast steel and contribute a significant part of the total weight of the railway car. In the rail line shipping industry, weight limits are placed on shippers of goods for preserving the safety and conditions of the track. Consequently, the quantity of goods that may be placed in or on a railcar is affected by the weight of the railcar body, the trucks and other railcar components. Thus, a reduction in the weight of the railcars, including the truck bolster, will result in an increase in the total capacity of goods shipped by a rail line owner. Therefore, it is highly desirable to reduce the weight of the truck bolster while at the same time maintaining the strength and fatigue resistance capabilities of the bolster.
Accordingly, an object of the present invention is to reduce the weight of a railway car by reducing the overall weight of the truck bolster. It is another object of the invention to reduce the weight of the truck bolster without a decrease in strength or fatigue resistance.
Briefly, the present invention involves removing metal from the compression and tension members of the truck bolster and locating a pair of vertical ribs on opposing sides of the bolster center bowl. The vertical ribs extend from the tension member to the compression member. The compression member has a wall thickness that is thinner than conventional bolsters near the center bowl and gradually increases in thickness from the center bowl to the ends of the bolster arms. Likewise, the tension member has a wall thickness that is thinner near the center of the bolster and which gradually increases in thickness toward the ends of the bolster arms. Both the tension and compression members are continuous without lightener holes. To compensate for the loss of material and resulting strength in the compression and tension members, the transversely extending vertical ribs are added on opposing sides of the center bowl to provide the required structural strength to the bolster. Significantly, the disclosed bolster is lighter than conventional truck bolsters, thereby creating an increase in the total capacity of goods that can be shipped by rail line owners. Specifically, the weight of the disclosed bolster has been reduced by over 230 pounds, translating into a weight reduction of over 46,000 pounds for a typical 100-car train. This significant weight reduction, in turn, translates into a significant increase in goods which may be shipped by rail line owners.
In addition, the disclosed light weight truck bolster is cast from a one-piece bolster core which offers several manufacturing advantages. Traditionally, three to five core pieces were used which led to problems during the pouring process, such as, core shifting. Core shifting, in turn, led to dimensional inconsistencies and greater wall thicknesses which, consequently, led to an increase in the weight of the bolster. These problems are eliminated with a one-piece core. Also with a one-piece core, the bolster wall thickness can be reduced without the possibility of multi-core shifting which, in the past, has created walls that were too thin. Moreover, in addition to the increased manufacturing efficiency with a one-piece core, chaplets which typically were used to support multi-cores are no longer needed to support the cores. Instead, the mold supports the one-piece core. Without the use of chaplets, associated problems, such as, the creation of stress concentrations and removal of chaplet scars in finishing are eliminated. Moreover, significant savings in the costs associated with finishing the bolsters are realized.
The full range of objects, aspects and advantages of the invention are only appreciated by a full reading of this specification and a full understanding of the invention. Therefore, to complete this specification, a detailed description of the invention and the preferred embodiments follow, after a brief description of the drawings.